[1/2] QMP: Update README file

Message ID 1279810021-11875-2-git-send-email-lcapitulino@redhat.com
State New
Headers show

Commit Message

Luiz Capitulino July 22, 2010, 2:47 p.m.
A number of changes I prefer to do in one shot:

- Add a note about instability
- Add multiple monitors example
- Add 'Development Process' section
- Small clarifications

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
 QMP/README |   67 +++++++++++++++++++++++++++++++++++++++++------------------
 1 files changed, 46 insertions(+), 21 deletions(-)


diff --git a/QMP/README b/QMP/README
index 35a80c7..8618c6f 100644
@@ -5,44 +5,52 @@  Introduction
 The QEMU Monitor Protocol (QMP) allows applications to communicate with
-QEMU's Monitor.
+QEMU's Monitor the right way.
-QMP is JSON[1] based and has the following features:
+QMP is JSON[1] based and currently has the following features:
 - Lightweight, text-based, easy to parse data format
-- Asynchronous events support 
-- Stability
+- Asynchronous messages support (ie. events)
+- Capabilities Negotiation
-For more information, please, refer to the following files:
+However, QMP is still under heavy development and is considered an unstable
+protocol. This means that its interface is going to have incompatible changes
+between QEMU releases. We plan to make QMP stable as soon as possible.
+For detailed information on QMP's usage, please, refer to the following files:
 o qmp-spec.txt      QEMU Monitor Protocol current specification
-o qmp-commands.txt  QMP supported commands
+o qmp-commands.txt  QMP supported commands (auto-generated at build-time)
 o qmp-events.txt    List of available asynchronous events
 There are also two simple Python scripts available:
-o qmp-shell       A shell
-o vm-info         Show some information about the Virtual Machine
+o qmp-shell  A shell
+o vm-info    Show some information about the Virtual Machine
 [1] http://www.json.org
-To enable QMP, QEMU has to be started in "control mode". There are
-two ways of doing this, the simplest one is using the the '-qmp'
-command-line option.
+To enable QMP, you need a QEMU monitor instance in "control mode". There are
+two ways of doing this.
+The simplest one is using the '-qmp' command-line option. The following
+example makes QMP available on localhost port 4444:
-For example:
+  $ qemu [...] -qmp tcp:localhost:4444,server
-$ qemu [...] -qmp tcp:localhost:4444,server
+However, in order to have more complex combinations, like multiple monitors,
+the '-mon' command-line option should be used with the '-chardev' one. For
+instance, the following example creates one user monitor on stdio and one
+QMP monitor on localhost port 4444.
-Will start QEMU in control mode, waiting for a client TCP connection
-on localhost port 4444.
+   $ qemu [...] -chardev stdio,id=mon0 -mon chardev=mon0,mode=readline \
+                -chardev socket,id=mon1,host=localhost,port=4444,server \
+                -mon chardev=mon1,mode=control
-It is also possible to use the '-mon' command-line option to have
-more complex combinations. Please, refer to the QEMU's manpage for
-more information.
+Please, refer to QEMU's manpage for more information.
 Simple Testing
@@ -59,8 +67,25 @@  Escape character is '^]'.
 { "execute": "query-version" }
 {"return": {"qemu": "0.12.50", "package": ""}}
+Development Process
+When changing QMP's interface (by adding new commands, events or modifying
+existing ones) it's mandatory to update the relevant documention, which is
+one (or more) of the files listed in the 'Introduction' section*.
+Also, it's strongly recommended to send the documentation patch first, before
+doing any code change. This is so because:
+  1. Avoids the code dictating the interface
+  2. It's very likely that the interface will change during review, updating
+     the code at the same time might be a big waste of time
+* The qmp-commands.txt file is generated from the qemu-monitor.hx one, which
+  is the file that should be edited.
-Luiz Fernando N. Capitulino <lcapitulino@redhat.com>